Pneumatic bumping tool for sheet metal



Dec. 4, 1934. c. HOPKINS PNEUMATIC BUMPING TOOL FOR SHEET METAL 2 Sheets-Sheet l in d M V Filed D90. 26, 1931 lla-kill!) link!!! 1 1934- c. HOPKINS PNEUMATI'C'BUMPING TOOL FOR SHEET METAL Filed Dec. 26, 1951 2 Sweets-Sheet 2 INVENTOR V Sa a/14 ATTORNEY Patented Dec. 4, 1934 I 1,982,667 A PNEUMATIC BUMPING TOOL FOR SHEET METAL Charles Hopkins, Detroit, Mich.

Application December 26, 1931, Serial No. 583,266

5 Claims. '(Cl. 153-32) This invention relates to pneumatic hammering or bumping tools, and more particularly to a tool of this nature which is adapted to the straightening of irregularities in sheet metal, such as auto-.

mobile fenders, etc., by hammering, being an improvement upon the invention disclosed in my copending application, Serial Number 470,834, filed July 26, 1930, Patent No. 1,934,979, dated November 14, 1933.

An important object of this invention is the provision of such a pneumatic bumping tool capable of operating with equal efficiency, and of delivering blows of equal force, despite wide variations of the pressure of the air or other motivating fluid supplied thereto, and yet in which the force of the delivered blow may be changed at will by the user to adapt the tool to varying conditions of use.

Another object of this invention lies in the provision of improved and simplified valvular controlling means for the intake and exhaust of the 'air or other driving fluid of the hammer.

It is also an object of my invention to provide such a pneumatic sheet metal bumping tool which in operation consumes but very little air and is capable of operating upon a relatively low air'pressure supply.

A still further object of this invention'lies in incorporating in such a device interchangeably replaceable hammer peens and cooperating anvils of novel construction and increased efficiency, especially effective for use upon sheet metal.

The provision of a novel and improved manner of conducting the air or other motivating fluid to the bumping tool is a still further object of my present invention.

Another object of this invention lies in the-provision of such a tool, particularly adapted to the straightening of fenders, which ,can be used effectively by an unskilled workman, who can by its use perform a perfect straightening repair job upon a fender in far less time than a skilled workman could perform the task by hand.

Other objects and advantages will be apparent from the following description, wherein reference is made to the accompanying drawings illustrating a preferred embodiment of my invention, and wherein similar reference numerals designate similar parts throughout the several views.

In the drawings:

Figure 1 is a side elevational view of a bumping tool incorporating the principles of my lnvention;

Figure 2 is an end elevational view thereof taken looking substantially in the direction of the arrow 2 of Figure 1;

Figure 3 is a vertical sectional view taken substantially on the line 3-3 of Figure 2 and looking in the direction of the arrows, the clamplike supporting member being broken away;

Figure 4 is a horizontal sectional view taken substantially on the line 4-4 of Figure 2 and looking in the direction of the arrows, the suplooking in the direction of the arrows, showing the valve member so positionedthat the inlet ports are opened and the outlets closed;

Figure 8 is a similar sectional view taken substantially on the same line but showing the inlet ports closedand the outlets in opened position;

- Figure 9 is a perspective view of my preferred form of valve member;

Figure 10 is a perspective view of the piston and its associated parts;

Figure 11 is a perspective view of theadjusting member for varying the severity of the blow delivered by the hammer by adjusting the anvil positioning;

Figures 12, 13, and 14 are perspective views of various forms of interchangeable dollies or anvils;

Figure 13 is a vertical sectional view taken substantially on the line 15-15 of Figure 1 and looking in the direction of the arrows;

Figure 16 is a bottom plan view of the adjusting device for changing the vertical positioning of the interchangeable dollies, and

Figure 17 is a bottom plan view of the supporting member against which the adjusting device shown in Figures 11 and 16 seats.

Referring now to the drawings: Reference character 10 designates a supporting member in the form of a generally C- shaped clamp, the extremity of one leg 11 of which supports my improved pneumatic hammer construction, the hammer or peen-carrying portion 12 of which is relatively rapidly projected toward and, retracted from the extremity of the opposite leg 13 of the supporting member when the tool is in operation. The extremity of the opposite leg 13 ward pressing of a plunger.

of the supporting member carries a dolly or anvil 14 rigidly but adjustably secured upon its inner surface in substantial axial alignment with the hammer 12, against which dolly the force of the blow delivered by the hammer is intended to be spent.

The construction of the supporting clamp is best shown in Figures 1 and 2, and although its details are of course more or less optional, I preferably form it of one of the relatively strong aluminum alloys, so contoured that a slight clearance drop is provided in the lower leg 11, which permits easy manipulation of the device about a fender. The innermost portion of the c is preferably thickened, for strength, as at 10', and this portion of the lower leg 11 of the clamp may be cored when the clamp is cast, to provide an air passage therethrough by means of which the motivating air supply may be conducted to the tool. A valve 55 may be arranged in the air chan nel and carried directly by the clamp in the manner shown, by means of which the air supply may be controlled. I preferably so arrange the valve that it is closed when released, and may be opened to a greater or less extent by simple in- The air channel 33 terminates in the horizontal finished surface surrounding the socketed portion 11' of the lower leg 11 of the clamp, which portion is adapted to receive the hammer unit. The hammer unit is formed with an air passage terminating in an opening adapted to register with the terminal opening of the passage 33, when the hammer and clamp are assembled, to provide for conducting the air to the operative portions; of the tool, as will presently be more particularly described.

The pneumatic hammer or bumping unit comprises a hollow shell 26 formed with a cylindrical inner surface in which a piston 2'7 is slidable. The housing 26 rests in the socket 29 formed to receive it in the extremity of the leg 11 of the support, and carries a flange 28 projecting from its outer surface by means of which it is secured by bolts 30 and nuts 31 to the portion 29 of the supporting clamp. A gasket 32 is preferably interposed between the opposed surfaces of the flange and the top of the leg of the support against which it bears, these surfaces being preferably smoothly finished. The air passage 33 in the clamp, as above stated, terminates adjacent the socket 29, and beneath the flange 28. Above the flange and in alignment with the aperture 33,

the housing 26 is formed with a passageway 34 extending upwardly therefrom and formed in an integrally cast projecting portion on the side of the housing. At its upper extremity the passageway turns inwardly and terminates adjacent and outside the ring 35 which is forced or otherwise rigidly secured in the upper enlarged portion of the cylinder 36. The ring 35 is provided with an accurately cylindrical inner surface, and the rotatable annular sleeve valve 36 is journaled and accurately fits directly within the ring 35, the fit between the two rings being a close slidable one. The inner surface of the sleeve valve substantially conforms in diameter to the cylinder. The ring 35 in which the sleeve valve 36 is journaled is formed with an inlet port 37 at the termination of the passage 34, and the valve carries a complementary inlet port 38 which may register therewith when the valve is rotated to the proper position. The rings 35 and 36 are also formed with a plurality of outlet ports 39-40, which are also alignable with each other, but only when the inlet ports 37-38 are in disalignment and the inlet thus also of the cylinder.

consequently closed. I preferably form all of the inlet and outlet ports 37, 38, 39, 40 as relatively narrow vertical slit-like apertures, so that full opening and closing of the inlet and outlet ports may be quickly obtained by short valve travel. If desired, the ports in the valve ring may be formed slightly wider than those in the ring 35, so that full opening and closing may be assured even if long use and consequent wear should render the fit between the two rings a relatively loose one. This is not at all necessary, however,

as the,wear between these parts is extremely slight, due to the short valve travel, floating valve construction and absence of heat.

Integral with the top of the piston-27 may be formed a cylindrical cam-supporting portion 58 of reduced diameter, in which the box cam 41 may be directly cut, although obviously attached guides might be used if desired. The track formed by the walls of the cam slot is best shown in Figure 10, and is so contoured as to shift the sleeve valve by means of a follower pin 43 carried by and projecting inwardly from the valve. Reverse throws occur as the piston approaches the top and bottom of its stroke. The piston 27 and cam support 58 are prevented from rotating, and forced to reciprocate in a rectilinear path by the key 44 carried by the wall 26 of the-housing, from which it projects inwardly through a clearance slot 42 in the valve ring, which slot is formed large enough to permit free movement of the valve without its engaging the key. The key 44 is formed with a threaded end 44' by means of which, and the nut 44, it may be secured in the housing. Its other squared end engages in the straight key-way 47 formed in the portion 58 carried by the piston, which is thus prevented from rotating, thereby forcing the piston to travel a rectilinear path. The piston 2'7, cam support 58, and hammer 12 may if desired be rigidly secured together and formed unitarily.

The cap 50, secured as by screw threads to the top of the housing 26, serves as a cylinder head and is provided with an axial aperture and a stuffing box 51, through which the cylindrical hammer 12 is slidable. The take-up screw 52 for the stufllng box may be positioned inside the head 50, as shown in Figure 3. The piston may be provided with a sealing ring, as 53, if desired, and the piston and hammer are normally urged upwardly and outwardly respectively by the relatively heavy compression spring 54 which bears upwardly against the inside of the portion 58 carried by the piston and downwardly against the cap 48 which closes thebottom of the socket and The cap is formed with breather ports 46 therein, and a boss 49 may also be provided to position the spring 54.

When the piston is descending, and in the position shown in Figure 5, the surface 41 of the cam is engaging the pin 43, to so shift the sleeve valve as to close the inlet port and open the exhaust ports, which movement is completed as the piston approaches the bottom of its stroke. The spring 54 then forces the piston upwardly and the hammer delivers its blow against the dolly 14 or whatever may be interposed. As the piston approaches the top of its stroke, and slightly before it is reached, the surface 41' of the cam engages the other side of the pin 43, and so shifts the sleeve valve in the opposite direction, to close the exhaust ports and open the inlet port. The air which is forced into the space above the piston due to the slightly premature closing of the exhaust ports and opening of the intake port serves to cushion the end of the stroke in a manner well known in the design of pumps and reciprocating engines of various sorts. The effectiveness with which the air above the piston cushions the stroke willbe seen to be dependent upon the length of the stroke after the exhaust is closed and the intake open, so that the longer this portion of the stroke may be, the farther the piston may travel before delivering its blow, thereby allowing a greater quantity of air to enterto cushion the same.

' To vary the length of the stroke and thus the severity of the delivered blow, provision is made for adjusting the dolly 14 toward and away from the hammer carried by the opposite leg of the support, since the dolly limits the length of the stroke. Such adjustment is secured by means of radial notches 15, 16 and 17 of graduated depth formed in the upper surface of the supporting member 56 for the dolly, as shown in Figure 11. The supporting member 56 is rotatable upon but irremovable from the stem of the screw 21. The notches are so arranged that those of equal depth are disposed at angles 'of ninety degrees with respect to each other. The notches are therefore arranged in sets of four,

, and all notches of each such set are of equal depth. In the described and illustrated arrangement all of the notches are of equalwidth, those designated 15 being of greatest depth, while the notches 17 are shallowest. The notches are arranged to seat, one set at a time, upon four blocks 18 carried uponthe inner extremity of the upper leg 13 and designed to fit in the notches. The blocks are here shown formed as integral projections upon a hardened plate 19, as of steel, rather than directly upon the supporting member itself, which may as above stated be formed of one of the stronger aluminum alloys in the interest of lightness. An axial aperture, as 20, is formed in the adjusting member 56 and a clamping screw 21 extends freely therethrough, and through an aperture 22 in the supporting arm 13. The clamping screw may be manipulated by a knob 23, and it will be seen to project beyond the member 56, which projecting portion is threaded for the removable attachment thereto of any of various dollies formed of diverse contours for convenient working upon fenders or other sheet metal of varying configuration, When the adjusting screw is tightened, the dolly, stepped block 56 and plate 19 are tightly clamped together, while loosening the screw not only permits removal of the dolly but allows the projecting portions .of the member 56 to clear the blocks 18 carried by the plate 19, so that the member 56 may then be turned to bring any desired set of notches into alignment with the blocks and clamped in that position by tightening the screw into whatever dolly may be desired to be used. Any suitable indicia may be im ressed upon the dolly and the support or the plate 19 to indicate the adjustment of the dolly. The letters L", M, and H indicating light, medium, and heavy, are shown stamped upon the plate 56, together with suitable indicating lines 24 and another line 25 for cooperation therewith is stamped upon the edge of the plate 19. Cooperating interfitting studs and apertures may be formed upon the dolly O and member 56 as shown in Figures 15 and 16, to

prevent turning of the dolly from its desired position of use. This is of course desirable with dollies of special configuration, and as shown in Figures 15 and 16, in which the studs are designated 57 and the apertures 59, three of the latter may be provided conforming to the three possible positions of the member 56, enabling turning the dolly to the proper position no matter how the blow may be adjusted by means of the member 56.

The functioning of the vertically adjustable dolly construction will from the above be clearly apparent, this adjustment being so arranged that by so turning the member 56 that it seats upon notches of varying heights the permitted length of the hammer stroke and consequently the stroke of the piston may be varied-sufficiently to effect desired changes in the cushioning and therefore the strength of the blow.

The cam track and the shape of the intake and exhaust ports will be seen to be so designed as to provide a quick and full opening of the ports with a minimum valve movement, which makes for greater efficiency and longer wear of the moving parts. Provision of theinitially separate inset port ring 35 enables cutting the rectangular ports in the ring rather than in the shell 26 itself, which latter therefore needs only to have apertures therein of sufficient size for unrestricted air passage outside the ports. This cam and valve construction will be seen to be further characterized by the fact that the valve is entirely floating, in that no means are provided for locking the valve in either position, other than its resistance to reverse movement. This enables an extremely simple, novel and effective cam and valve actuating construction, as will be apparent. Running the air supply line to the bumping unit through the support rather than through an outside pipe or tube not only'guards the same against injury but provides greater room between the arms of the support, so that the same may be freely passed over intervening objects or portions of the metal being worked upon, as the edges of fenders, etc.

I preferably form the hammer in a manner to enable the interchangeable secural of peens of various forms thereto, as by forming the peens with stems adapted to be frictionally secured in a suitableaperture in the end of the hammer 12, as by the resilient ring 60 adapted tosnap into a groove 61 formed on the stem of the peen, after which its partial engagement in that groove and its partial engagement in the relatively deeper groove 62 in the hammer, locks the peen 63 in position, although it may be removed by simple prying, which forces the ring to expand against its normal resiliency, into the groove 62. Insertion of the stem of the peen may be facilitated by chamfering its lower extremity. Peens of ovate form will be found most eflicient for certain work, while flatpeens will serve best in other cases.

In the ordinary hand operation of straightening a fender, the workman knocks up from below with a sledge hammer or the like any indentations therein, and the practise is to knock such dents higher than is necessary. This is termed the roughing operation. The workman then carefully finishes the smoothing of the fender by hammering from above while constantly holding a dolly beneath the point at which he is striking. Of course trouble is encountered whenever points are left which have not been knocked high enough in the roughing operation. Furthermore it requires a skilled workman to perform the finishing operation. My tool is arranged to perform the finishing operation by striking a fender from below while the dolly is held above. This arrangement not only eliminates the possibility of low spots remaining in the finished job, but enables merely resting the dolly upon the: fender, and thus allowing the work to bear the weight of the tool. An ordinary unskilled workman can in this fashion perform the entire smoothly finished bumping operation, using my improved tool, in much less time than the same work could be done by a skilled workman. Whether the initial roughing operation is performed by hand, or whether the tool is usedfor both roughing and finishing, it will perform with equal efficiency, although a heavy sledge may be used if desired to speed the initial roughing process. V

While it will be apparent that the illustrated embodiment of my invention herein disclosed is well calculated to adequately fulfill the objects and advantages primarily stated, it is to be understood that the invention is susceptible to variation, modification and change within the spirit and scope of the subjoined claims.

What I claim is? 1. In a pneumatic hammering tool for sheet metal, a support of generally C-contour, a pneumatic hammer unit carried by one leg of the support, an anvil member carried by the other leg and adapted to receive the blows delivered by the hammer, and means for varying the strength of the blow delivered by the hammer comprising adjusting means for moving the anvil to and rigidly fixing the same in positions variantly distant from the hammer, and including a backing plate having portions of variant thicknesses, and

means for clamping the anvil member and backing plate together and against the supporting leg with said plate in different positions, whereby portions thereof of variant thicknesses separate the anvil and the leg.

2. In a pneumatic hammering tool for sheet metal, a support of generally c-contour, a pneumatic hammer carried by one leg of the support, an anvil member carried by the other leg against which the force of the blows of the hammer are adapted to be spent, and means for varying the strength of the blows delivered by the hammer comprising a support for the anvil, including backing portions of varying heights carried by the support against which the anvil is adapted to seat, and means for clamping the anvil against the backing portions of varying heights, to enable-its securance at points variant in distance from the hammer.

3. In combination with a percussive pneumatic tool having a piston and a reciprocating member actuatable thereby, a generally C-shaped support upon one leg of which the tool is mounted, anvil supporting means carried by the other leg opposite the tool, a dolly adapted to be secured to the anvil supporting portion, said portion and the dolly having complementarily formed engaging surfaces parts of which are of different heights, and means for securing the dolly to the support in various relative positions, whereby its distance from the tool may be varied.

4. In combination with a percussive pneumatic tool having a piston and a reciprocating member .actuatable thereby, a generally 'C-shaped support surfaces, parts'of which are of different heights,

and means for securing the dolly to the support in various relative positions, including a shaft rotatably passing through said engaging parts and threaded into the dolly, whereby said engaging parts may be secured together and the dolly attached to the leg, and by loosening the dolly said engaging parts may be moved to different relative positions to change the distance between the dolly and the tool.

5. In combination with a pneumatic tool having a piston and a reciprocating member actuatable thereby, a generally c-shaped support upon one leg of which the tool is mounted, anvil supporting means carried bythe other leg opposite the tool and-having a discontinuous surface, a plate having acooperating surface adapted to engage that ofthe supporting means, at least one of said surfaces having portions of variant heights, a dolly, and means for securing the dolly in place, comprising a clamping screw extending through said engaging portions and the plate and threaded into the dolly, wherebywhen' the dolly is loosened the plate is released and may be turned to bring various parts of said engaging surfaces into contact, and when the dolly is tightened by means of the screw the surfaces are clamped together and the dolly attached to the leg.

CHARLES HOPKINS. 

